TAP reactor studies of the oxidizing capability of CO2 on a Au/CeO2 catalyst – A first step toward identifying a redox mechanism in the Reverse Water–Gas Shift reaction

As a first step toward elucidating the mechanism of the Reverse Water–Gas Shift (RWGS) reaction on a supported Au/CeO2 catalyst, in particular the role of the redox mechanism, we have investigated the ability and activity of CO2 for re-oxidizing a pre-reduced Au/CeO2 catalyst surface by quantitative temporal analysis of products (TAP) measurements. It is demonstrated that a surface-reduced Au/CeO2 catalyst can be (partially) re-oxidized by exposure to CO2 pulses and that the surface oxygen deposited this way can be reactively removed again. The probability for oxygen deposition from CO2, however, is significantly lower than that from O2. Both the low reaction probability and the temperature dependence of oxygen deposition from CO2 point to an activated step. Implications of these results for the mechanism of the RWGS reaction are discussed.